High demands are increasingly being placed on internal combustion engines in terms of their performance and efficiency. At the same time, the emissions also have to be low due to strict legal regulations. Demands of this kind can readily be satisfied if the internal combustion engine is fitted with gas exchange valves and corresponding drives for said valves, in which the valve-lift response differs depending on the operating point of the internal combustion engine. In this way, throttle losses upon intake of air can be reduced and, optionally, high exhaust-gas recirculation rates rapidly adjusted.
Thus, it is known, for example, for the valve lift of a gas inlet valve of the internal combustion engine to be adjusted between a low and a high lift. Furthermore, it is also known for the phase relation between the valve lift of the gas inlet valve and the valve lift of the gas outlet valve to be adjusted. Thus, for example, the Porsche 911 Turbo is fitted with a device for adjusting the phase relation between the valve lift of the gas inlet valve and of the gas outlet valve. Furthermore, the internal combustion engine of this vehicle is fitted with a camshaft on which for each gas inlet valve one cam with a low lift and two further cams with a higher lift are fashioned. The cam displacement is transferred by means of a transfer unit to the gas inlet valve. The transfer unit is fashioned as a cup tappet, which comprises a cylinder element and an annular cylinder element arranged concentrically in relation to said cylinder element. The cam with the low lift acts on the cylinder element while the cams with the higher lift act on the annular cylinder element. Depending on a switching position of the cup tappet, either the low or the high lift is transferred to the gas inlet valve. When the internal combustion engine is idling, the low cam lift is transferred to the gas inlet valve. As a result, reduced frictional losses occur due to the small diameter of the cam used in this operating state and to the cylinder element and to the lower valve lift.
Also, a higher charge movement is achieved. By this means, the emissions of the internal combustion engine can be cut and at the same time fuel consumption kept low. The low valve lift is maintained at low and medium charge. Throttle losses can additionally be reduced by a corresponding phase adjustment between the gas inlet valve and the gas outlet valve and an internal exhaust gas recirculation rate resulting therefrom. Where the charge requirements on the internal combustion engine are high, a switch is made to the higher valve lift.